SSR overheating, getting stuck "on".

spaceship · Joined: 31 Jul 2014 Posts: 2

Building my control panel and upon testing the ssr works fine, switching the element on and off when the PID cycles on or off, but when bringing up temp in the HLT, where the heating element is constantly on for some time, my SSR and heat sink are getting very hot (too hot to touch) and eventually when the set temp is reached and PID switches off, the element stays on, the SSR is stuck on. turning the power off and letting the SSR cool down it returns to normal function. If I operate it with a fan pointed at the heat sink to keep it cool it works fine.

I bought a cheap Fotek SSR with a small heat sink, photo attatched. I have seen other builds using these smaller heat sinks, so my question is do they work well enough usually? Is my problem with the "cheap" SSR, or are these smaller heat sinks really not sufficient.

Heating element is 5500W.

**kal** · Posted: Tue Nov 18, 2014 8:51 pm Post subject:

I never found those sized heat sinks large enough for 5500W without some sort of fan (which I didn't want in order to keep my control panel water resistant/industrial/outdoor proof).

Do you have this heatsink in an enclosed space like inside an enclosure? That would only make it worse and heat up everything else in the enclosure, shortening the lifespan of the other items too. If it is in a small enclosed space, I would put it outside the enclosure and try without a fan first. If it's already outside the enclosure then adding a fan should work if you're ok with it not being water resistant/industrial/outdoor proof. If you don't want to compromise water resistance, a larger heatsink such as this one outside the enclosure is your best option: http://www.theelectricbrewery.com/custom-heat-sink

Good luck!

Kal

ChukInaTruk

James Edmonton · Posted: Wed Nov 19, 2014 5:44 am Post subject:

I run the smaller 2500 watt elements and the heat sinks you are showing work fine for that wattage of elements. I ran mine out the top of the box - which isn't the greatest aesthetic but it works. They get warm to the touch but that is it. I don't need a fan, but if I mounted them in the box (the original plan) a fan would be a good idea. At some point, I will probably change the heat sinks to something that has a lower profile and looks better.

As Kal notes, he probably has more heat sink that he needs, but in this case cooler is always better and should extend the life of the SSRs.

foomench · Posted: Wed Nov 19, 2014 5:34 pm Post subject:

Here's a question related to these smaller heatsinks and placement. I'm going to use one for my 120V, 1500 watt element. Right now the heatsink is attached directly to the SSR, as I had thought of putting it inside the box. But I already decided it needed to be external. Now the question is:
A) Do I cut a hole in my metal box and just poke the heatsink through, still attached to the SSR, or
B) Do I attach the SSR to the inside of the metal box, and put the heatsink on the outside, directly over the SSR?
Kal's approach is A. But with my little heatsink, I'm wondering how well I'll be able to seal it, since I don't have the borders of Kal's oversize heatsink to run silicon sealant around. B will be much easier, but essentially makes the entire enclosure part of the heatsink, and perhaps diminishes the usefulness of the actual heatsink as it is no longer directly coupled to the SSR.

Kevin59 · Posted: Wed Nov 19, 2014 6:26 pm Post subject:

James Edmonton · Posted: Wed Nov 19, 2014 6:45 pm Post subject:

I mounted mine through the top like this. Essentially you make a hole (square) that is a wide as the heatsink but not as deep as the mounting plate. drill two holes for the mounting screws. You can then place the heatsink into the case from the top by working it back and forth. Then you attach the SSR to the heatsink and work it back out to the mounting plate and add the screws. From the inside out you end up with the SSR-heatsink-case configuration. You can then caulk the edges to seal it all up. I haven't caulked mine yet as I was waiting to see about performance before I committed to the final placement. It is located where there is a very remote possibility of spray now, but I will caulk it soon (as I am hope to move it closer soon).

The pictures should help explain it. It is not as nice as a single larger heatsink, but it is very functional. I have a 5 gal system (converted from propane) so I only use 2500 watt 240v elements, which work fine. The heat sinks (even when both elements are running) only get warm.

In the case of a single 120v 1500 watt element you might be fine mounting it inside as it should not get very warm. You could start there and see what happens and move it outside of it looks like it will be a problem.

foomench · Posted: Wed Nov 19, 2014 9:35 pm Post subject:

Thanks James for the explanation and photos. I think I'm going to try something like your approach this first. Then I might resort to the heatsink that Kevin linked. I had already bookmarked that one from the simple controller thread. Kal instructions mention cutting two holes for heatsinks like these, but then his instructions focus on the larger heatsink for actually mounting things. Since that's what he did, this is understandable. It's helpful to have the rest of the story for the smaller dual heatsink option.

Kazumichan · Posted: Thu Nov 20, 2014 2:40 am Post subject:

If anyone is interested, I have a large heatsink that would work for two SSR's. It just needs drilled and tapped for them. http://www.theelectricbrewery.com/forum/viewtopic.php?t=27485

TheMadZymurgist · Joined: 16 Oct 2014 Posts: 6 Location: Southern Indiana

I'm going to ask the painfully obvious and silly question here. I didn't see any mention of heat sink compound in your description of how you mounted these. You did use some, right?

foomench · Posted: Thu Nov 20, 2014 4:36 pm Post subject:

I don't know what spaceship did, but I think I my heatsink came with some thermal compound. If not, I used some CPU cooler stuff like Arctic Silver. I know I used something.

huaco · Joined: 05 Apr 2012 Posts: 1506 Location: Burleson Texas

foomench · Posted: Thu Nov 20, 2014 7:27 pm Post subject:

huaco · Joined: 05 Apr 2012 Posts: 1506 Location: Burleson Texas

James Edmonton · Posted: Sat Nov 22, 2014 5:19 am Post subject:

Yes, I did use thermal compound - if you don't you seriously compromise the effectiveness of the heatsink. I don't know what Spaceship decided to do, but I hope he uses thermal compound as well! Smile

Sketchin · Joined: 08 Jan 2013 Posts: 169 Location: Calgary

foomench · Posted: Mon Nov 24, 2014 5:31 pm Post subject: